第一关String类

package step1;

import java.util.Scanner;

public class StringLearning {

    public static void main(String[] args) {

        Scanner scanner = new Scanner(System.in);
        String stringExample = scanner.next();
        String endStr = " end";
        // ---------------------Begin------------------------
        int len =stringExample.length();

        System.out.println("原字符串为："+stringExample);
        System.out.println("字符串长度为："+len);
      
        System.out.println("转换成大写字符串："+stringExample.toUpperCase());
          System.out.println("转换成小写字符串："+stringExample.toLowerCase());
   System.out.println("第3-7的字符串内容为："+stringExample.substring(3,7));
        System.out.println("字符串相加后:"+stringExample.concat(endStr));
       
       

      
      
        // ---------------------End------------------------

    }
}

第2关：StringBuffer类

package step2;

import java.util.Scanner;

public class StringBufferLearning {


    public static void main(String[] args) {

        Scanner scanner = new Scanner(System.in);
        String stringExample = scanner.next();
        // ---------------------Begin------------------------
       
    StringBuffer sb1=new StringBuffer(stringExample+"educode");
 System.out.println("添加数据后："+sb1);
     sb1.delete(5,8);
    System.out.println("删除5-8的字符串后："+sb1);
     sb1.replace(7,13,"world");
     System.out.println("替换7-13的字符串后："+sb1);

      System.out.println("截取1-10的字符串为："+sb1.substring(1,10));
     sb1.reverse();
      System.out.println("反转后的字符串为："+sb1);

       

        // ---------------------End------------------------

    }
}

第3关：Math类

package step3;

import java.util.Scanner;

public class MathClass {
    public static void main(String[] args) {

        Scanner scanner = new Scanner(System.in);
        int value1  = scanner.nextInt();
        int value2 = scanner.nextInt();
        // ---------------------Begin------------------------
        /**
         1.求出变量value1的绝对值
         2.求出value1的3次幂
         3.求出value1的二次方根
         4.求出value1的sin值
         5.求出value1与value2中的较大者
         * */
        System.out.println("value1="+value1+", "+"value2="+value2);
    
       int n=Math.abs(value1); 
       System.out.println("value1的绝对值为："+Math.abs(value1));
       double n1=Math.pow(value1,3);
       System.out.println("value1的3次幂为："+String.format("%.6f",n1));
       double n2=Math.sqrt(value1);
       System.out.println("value1的2次方根为："+String.format("%.6f",n2));
         double n3=Math.sin(value1);
       System.out.println("value1的sin值为："+String.format("%.6f",n3));
       System.out.println("value1与value2中的较大者为："+Math.max(value1,value2));
       

       
        // ---------------------End------------------------
    }
}

第4关：Random类

package step4;

import java.util.Random;

public class RandomClass {
    public static void main(String[] args) {

        // ---------------------Begin------------------------
       
       Random r = new Random(2022); // 不传入种子
        // 随机产生10个[0,100)之间的整数
        for (int x = 0; x < 5; x++) {
            System.out.println(r.nextInt());
        }

    for (int x = 0; x < 5; x++) {
            System.out.println(r.nextDouble());
        }


        // ---------------------End------------------------

    }
}

第5关：知识回顾

1D 2 正确 3 正确 4StringBuffer